The present invention relates to a structure of a through hole and a pattern of a multi-layer wiring board, and a design thereof.
In a high speed signal transmission circuit for transmitting a signal at a pitch equal to or more than a gigahertz, there are problems that a signal attenuation is increased in a board wiring, a cable and the like, and an influence of an impedance mismatch reflection is increased due to a parasitic capacity in a connected portion (a through hole) to an LSI, a part or the like. As a prior art for reducing the influence of the reflection in the through hole portion, there has been a technique that the parasitic capacity of a stub in the through hole 1 is removed by drilling a hole in the stub portion of the through hole 1 by a back drill 9 as described in PCT WO 01/56338 A1, for example, shown in FIG. 2A. Further, there has been a technique using a BGA connection portion 12 and a micro via hole 10 without using the through hole as shown in FIG. 2B.